Energy management systems (EMS) provide automatic control of electrical loads—most commonly heating, ventilating and air conditioning (HVAC) systems and sometimes lighting. Building automation systems (BAS) include the energy management functionality of an EMS along with nonenergy-related loads, such as security and fire safety.

Although automatic lighting shutoff has become more important because of energy codes, only a small fraction of currently in-stalled EMS are used to control lighting. This is changing, creating a question for contractors and other lighting and control system designers: How can lighting management system (LMS) functionality be added to a new building? What is the best way to implement LMS and EMS together? And can lighting controls be coupled to an existing EMS? Integration is how.

An EMS is ideally suited for controlling large numbers of switched loads throughout a building and providing other services, such as maintenance scheduling, monitoring, logging and inventory control. An EMS that controls HVAC is installed in only about one in 18 commercial buildings, but those buildings represent nearly one-fourth of all commercial floorspace, according to the U.S. Department of Energy (DOE, 2003). EMS are most commonly found in office and education buildings of more than 100,000 square feet.

Only a small fraction of EMS in the installed base actually control lighting, according to the DOE. EMS that control lighting are installed in only 1.3 percent of buildings covering 7.4 percent of all commercial building floorspace.

John A. Bagwell, director of Synergy Lighting Controls, an Acuity Brands Co., Conyers, Ga., said there is a simple explanation for this missed opportunity: the construction design process is typically just as fragmented as building control functions.

“Lighting control design is generally specified by electrical engineers through Division 16, while EMS are specified by mechanical engineers through Division 15,” he said. “Few design firms coordinate the integration of these two disciplines.”

Arguably, demand traditionally has been lower for lighting control on a whole-building scale, which is why so many skylines are still lit by empty buildings during the night. But that is changing for two reasons, both of which can be summed up in a single word: energy.

More than 35 state commercial energy codes in the United States now require interior lighting to be automatically turned off when not in use. Accepted methods include load scheduling (using a system, such as an LMS), occupancy sensors, or a signal from another building system, such as an EMS (or one of its coordinated subsystems).

“There is a misperception that high-efficiency lighting negates the need for comprehensive controls,” he said. “Even energy-efficient lighting wastes energy if it is left on when it is not being used. The purpose of a modern lighting control system is to tailor lights to oc-cupancy and use—shutting off lights in unoccupied spaces and turning off the lighting in unoccupied buildings. Lighting control is an essential part of a modern energy management strategy.”

When designing a new building, there essentially are two choices. The designer could specify a stand-alone control system for light-ing, HVAC and other building systems or take a whole-building approach using a single system that does everything. One advantage of a whole-building approach is that, theoretically, it enables more cross-system functionality. For example, at the end of the day, when the last employee leaves and arms the security system, the security system could communicate this status to the EMS, which in turn would signal a lighting controller to deactivate the lights. Another advantage is the building operator can theoretically control an entire build-ing’s lighting from a single workstation and will not have to learn and use multiple software programs.

A potential disadvantage of the whole-building approach, however, is that a traditional EMS may not work well with some lighting control inputs and strategies, such as occupancy sensing, daylighting control and networked digital switches. And the EMS may not be able to respond quickly to inputs or control dimmable lighting loads, making a robust role for lighting in a demand response program difficult to achieve.

“Most EMS are very capable of sophisticated temperature control and, if it provides lighting control, can handle basic on/off operation for simple applications, such as controlling outdoor lighting via a photosensor,” Bagwell said. “For more application-specific lighting con-trol requirements, such as architectural dimming, daylighting control and other needs, an LMS solution will be needed.”

He points out that for these reasons, EMS manufacturers are turning to LMS manufacturers to provide robust lighting control func-tionality with open protocol communication, enabling integration without the addition of intermediary devices called gateways. Popular protocols include American Society of Heating, Refrigerating and Air-Conditioning Engineers’ (ASHRAE) BACnet and Echelon’s Lon-Works, promising cross-vendor interoperability as well as support by a significant number of companies in the EMS and LMS industries. Synergy and Square D/Schneider Electric, for example, offer native BACnet LMS solutions that promise reliable integration.

But even with an EMS and LMS sharing an open protocol, there may be integration issues. For example, BACnet was not originally de-signed to specifically accommodate lighting control. Dawn/dusk scheduling events, architectural dimming, blink warnings before shutoff, and other functions are not available in the current BACnet objects, for example (but may be addressed in future versions of the standard). The bottom-line result is the lighting control points can be mapped to the EMS and then controlled and monitored from the EMS work-station, which is the main prize. But the actual programming of most of the LMS features, where the majority of the integration work takes place, must occur at the LMS lighting control panel.

“In time, I believe the open protocols will develop to the point that most or all of the lighting control system features can be pro-grammed from the EMS workstation,” Bagwell said. “Until that time arrives, lack of programmability will be a frustration for end-users of EMS-integrated lighting controls.”

While EMS companies may be taking a new interest in lighting control, and in some cases turning to LMS companies for solutions, some LMS solutions may provide basic EMS functions. Even below the LMS level, this is possible. For example, occupancy sensors and power packs are available with an isolated relay for control of an interfacing with additional loads, such as HVAC and security sys-tems. At the LMS level, lighting control panels are available with outputs that can handle lighting and HVAC, service water heater and motor loads, thereby satisfying many of the functions required in ASHRAE 90.1 Section 6.4, such as automatic shutoff of HVAC (6.4.3.2.1) and dampers (6.4.3.3.3).

“The power of integration lies in fully utilizing the investment in new equipment and the enhanced functionality of having control across applications,” Hickerson said. “Employing lighting control systems to control other types of loads can be effective, but the ef-fectiveness depends greatly on the application.”

What if the EMS and LMS aren’t designed according to the same open protocol, which is often the case in an existing building upgrade project? Hundreds of buildings still use legacy systems, some of them analog systems going back to the 1960s. In such cases, Hickerson said the first consideration should be whether the older EMS ought to be replaced with a newer system.

“Since the older EMS probably paid for itself years ago, investing in a newer EMS with increased capabilities will achieve greater en-ergy savings,” he said.

The alternative is to find a gateway, which is a device enabling the legacy EMS and the new LMS to communicate and become interop-erable as a larger building system. In some cases, a gateway already may be in use to provide communication between two different EMS residing in the same building, or a gateway may be necessary for communication with specialized lighting control systems, such as DALI-based digital lighting systems.

“The advantage of a gateway in an existing building upgrade scenario is a lower upfront cost but possibly at the expense of lower en-ergy savings, reduced functionality and, most likely, multiple user interfaces,” Hickerson said.

“In many cases, the lighting circuits in an existing building do not match up with the temperature zones,” Bagwell said. “Centralized control of a lighting circuit in an electrical closet may affect multiple temperature zones. In such cases, distributed lighting controls are an ideal solution because the controller is moved from the electrical closet out to the area of control. Locating the lighting controller in the same area as the HVAC controller will help to better align the lighting and temperature zones and use the existing line-voltage wiring, thereby eliminating the need for line-voltage and low-voltage runs back to the electrical closet.”

The trend in building controls is integration. Within the lighting segment, control functions are becoming increasingly able to be in-tegrated with each other, EMS and lighting equipment, such as fixtures. As integration intensifies, in some cases, it may make design and specification easier, but in others, it may in turn require integration of the design process—closer collaboration among the project’s designers and contractors, Bagwell said. Successful integration of an EMS and LMS requires careful and early coordination among the electrical and mechanical engineers, contractors and building owner to properly estimate the required labor, produce a successful de-sign, and properly install and commission the building’s control system.

“When the details are worked out upfront during the design process and both contractors understand their respective responsibili-ties, then the chances for a successful integration project are very high,” Bagwell said.

DILOUIE, a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at www.zinginc.com.